There is a need for embedding data within other data. For example, for copy protection of entertainment content on digital media, there is a need to distribute decryption keys and copy control information along with the entertainment content. Decryption keys and copy control information may be recorded in reserved areas of a medium. Reserved areas may preempt space that could otherwise be used for user data. Alternatively, copy control information may be embedded within the entertainment content in the form of a digital watermark. Digital watermarks modify the original data.
U.S. Pat. No. 5,699,434 (Hogan), and divisions of that patent (U.S. Pat. No. 5,828,754, U.S. Pat. No. 6,278,386, and U.S. patent application Ser. No. 09/855,889) disclose multiple ways of embedding data into encoded data in ways that do not modify the original data, and in ways that do not reduce the capacity for recording original data.
There is an ongoing need for additional methods of embedding data within other data without reducing or altering user data.